1. Field of the Invention
The invention relates to an electric junction box which is adapted to be mounted in a vehicle.
2. Background of the Invention
FIG. 8 is an exploded view of a conventional electric junction box. See JP 2006-121880 A. A case 202 is a case body 203, an upper surface of which is opened, a first cover 204 and a second cover 205 disposed such that the upper surface of the case body 203 is closed.
The case body 203 has a partition wall 206 therein, which divides the interior space of the case body 203 into two part-receiving chambers 207a and 207b. The partition wall 206 is defined by two walls 206a and 206b which are slightly spaced apart from each other. Any fluid such as water which penetrates into a gap or clearance between the two walls 206a and 206b can be drained out. Parts such as a relay block are respectively received in the part-receiving chambers 207a and 207b. The part-receiving chambers 207a and 207b communicate with each other via a communication pathway 209 which is formed by removing a part of the partition wall 206. A wiring harness is arranged via the communication pathway 209 between the two part-receiving chambers 207a and 207b. 
The first cover 204 is attached to the case body 203 so as to close the opening of one part-receiving member 207a. Fluid disposed over or adhered to the upper surface of the first cover 204 falls off between the two walls 206a and 206b or along the outside of the case body 203.
The second cover 205 is coupled to the case body 203 so as to close the opening of the other part-receiving member 207b. Fluid disposed on or adhered to the upper surface of the second cover 205 falls off between the two walls 206a and 206b or along the outside of the case body 203.
In the conventional electric junction box in which the interior space of the case body 203 is divided into the two part-receiving chamber 207a and 207b, as shown in FIG. 8, the partition wall 206 is defined by the two walls 206a and 206b which are slightly spaced apart from each other, and fluid adhered to the first cover 204 and the second cover 205 falls off between the two walls 206a and 206b. As such, fluid such as water can be drained from the electric junction box. For the above configuration, the conventional electric junction is made waterproof.
On the other hand, the inventors have investigated thermal insulation between the neighboring part-receiving chambers in the afore-mentioned conventional electric junction box. The inventors have found that heat generated from the part-receiving chamber is less transferred to the neighboring part-receiving chamber by adopting the above partition wall 206 formed of the two walls 206a and 206b. In other words, the partition wall 206 can be called as a double wall.
However, because the gap or clearance between the two walls 206a and 206b is very small or slight, the resulting thermal insulation effect is not thus advantageous. On the other hand, the greater the gap or clearance between the two walls 206a and 206b is, the greater the size of the case 202 is.